Sleep apnoea severity independently predicts glycaemic health in nondiabetic subjects: the ESADA study.

Obstructive sleep apnoea (OSA) is associated with increased risk of dysglycaemia but the intimate link of these conditions with obesity makes discerning an independent relationship between them challenging. Glycosylated haemoglobin (HbA1c) levels predict adverse cardiovascular outcomes in nondiabetics but there is a lack of population-level data exploring the relationship of HbA1c with OSA. A cross-sectional analysis of 5294 participants in the multinational European Sleep Apnoea Cohort (European Sleep Apnoea Database) study was performed, assessing the relationship of OSA severity with HbA1c levels in nondiabetic subjects, with adjustment for confounding factors. HbA1c levels correlated significantly with OSA severity in univariate analysis. Following adjustment for confounding factors, apnoea-hypopnoea index (AHI) (standardised β 0.158; p<0.001), along with nocturnal hypoxaemia, predicted HbA1c. Adjusted mean HbA1c levels were lower in the lowest AHI quartile (5.24%, 95% CI 5.21-5.27%) than in the second (5.37%, 95% CI 5.34-5.40%), third (5.44%, 95% CI 5.41-5.47%) or highest (5.50%, 95% CI 5.46-5.53%) quartiles. Subjects in the higher quartiles had significantly greater adjusted odds ratios of HbA1c level ≥6.0% than those in the first quartile. In stratified analyses, OSA severity predicted glycaemic health irrespective of sleep study modality, sex, obesity or daytime sleepiness. OSA severity independently predicts glycaemic health in nondiabetic subjects. Further studies should assess the impact of OSA treatment on glycaemic health and elucidate underlying mechanisms.